S234: CLINICAL-GRADE MBIL21/4-1BBL EXPANDED NK CELLS EXHIBIT STRONGER COMPETENCE COMPARED WITH PRIMARY NK CELLS AGAINST HCMV INFECTION
Authors: Q.-N. Shang, X.-X. Yu, Z.-L. Xu, T.-T. Han, J. Xie, Z.-Y. Fan, M. Zhao, X.-H. Cao, X.-F. Liu, Y.-H. Chen, M. Lv, Y.-Q. Sun, Y.-J. Chang, Y. Wang, L.-P. Xu, X.-H. Zhang, K.-Y. Liu, X.-Y. Zhao, X.-J. Huang
Journal: HemaSphere (2022)

Background: Cytomegalovirus (CMV) infection remains a common complication and leads to high mortality in subjects who undergo allogeneic hematopoietic stem cell transplantation (allo-HSCT). Human NK cells are the first lymphocyte recovering after allo-HSCT. Previous studies indicated the early NK cell reconstitution may be protective against development of HCMV infection post HSCT. Our previous data also showed that rapid reconstitution of IFN-γ secreted NK cells at day 15 post transplantation predicted lower HCMV reactivation. However, little is currently known about whether and how NK cells are responsible for preventing HCMV infection post transplantation. NK cell adoptive transfer is a promising method for cancer immunotherapy. Ex vivo mbIL21/4-1BBL expanded NK cells exhibited high cytotoxicity against leukemia cells. Nevertheless, whether expanded NK cells owned higher anti-HCMV function compared with primary NK cells in vitro and in vivo were still unknown. Aims: To investigate whether expanded NK cells owned higher anti-HCMV function compared with primary NK cells in vitro and in vivo and the efficacy of adoptive NK cells infusion to patients post HSCT to prevent HCMV infection. Methods: NK cells were firstly ex vivo expanded by K562-mbIL21/4-1BBL feeder cells. We compared not only the cytotoxicity against HCMV infected fibroblast but also the competence of inhibiting HCMV propagation and reducing HCMV infection between ex vivo expanded NK cells and primary NK cells. Then primary NK cells and expanded NK cells were adoptive infused to HCMV-infected humanized mice to investigate the ability to eliminate HCMV infection in vivo. At last, 20 patients post HSCT were enrolled in our clinical trial to explore the safety and efficacy of adoptive infusion of K562-mbIL21/4-1BBL expanded NK cells to protect from HCMV infection. Results: 1. Most activating receptors, cell adhesion molecule receptors and chemokine receptors exhibited enhanced expression on expanded NK cells (figure 1a). Expanded NK cells showed stronger cytotoxicity against HCMV infected fibroblasts and enhanced abilities to inhibit HCMV propagation compared with primary NK cells in vitro (figure 1b). 2. Both expanded NK cells and primary NK cells showed the ability to migrate to the spleen, liver, and lung and persisted in these target organs in HCMV-infected humanized mice. On day 14 post infusion, expanded NK cells showed higher percentage in tissues than primary NK cells. Moreover, mice with expanded NK cell infusion exhibited more effective HCMV elimination compared with primary NK cell infusion. 3. The cumulative incidence of HCMV and refractory HCMV infection for patients in NK infusion cohort were significantly reduced compared with control cohort (figure 1c). Total HCMV persisting time was shortened (14 (5-24) days vs. 17 (7-56) days, p=0.013). What is more, the absolute number of NK cells was higher for patients in NK cell infusion group than that in control group. Higher quantitative reconstitution, more matured NK cell phenotypes and stronger function were determined in patients with expanded NK cell infusion than those in control group. Image:Summary/Conclusion: Based on in vitro and in vivo studies, our data demonstrated that adoptive NK cells infusion exhibited stronger activities compared with primary NK cells against HCMV infection.